1. Field of the Invention
The invention relates to data transfer in a wireless telecommunication system and, more particularly, the identification of data types transferred within the data packets of a wireless telecommunication system.
2. Description of the Related Art
In wireless telecommunication systems, Push-to-talk (PTT) capabilities are becoming popular with service sectors. PTT can support a “dispatch” voice service that operates over standard commercial wireless infrastructures, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), and global system for mobile communications (GSM). In a dispatch model, communication between endpoints (end user devices) occurs within virtual groups, wherein the voice of one “talker” is broadcast to one or more “listeners.” A single instance of this type of communication is commonly referred to as a dispatch call, or simply a PTT call. A PTT call is an instantiation of a group, which defines the characteristics of a call. A group in essence is defined by a member list and associated information, such as group name or group identification. In the absence of a wireless multicast channel, each group is formed by the combination of separate point-to-point connections between each endpoint and application servers manage the call. Each endpoint is also known as a client.
FIG. 1 illustrates a prior art architecture 100 supporting PTT communications. The architecture includes the deployment of a single application server region in conjunction with a carrier's CDMA infrastructure and packet data network. Each region of the application servers is deployed over a specific portion of a carrier packet data network. The application server within the region may be routing traffic between one or more Packet Data Service Nodes (PDSNs) in the carrier network. A communication device 102 that supports the PTT feature is in communication with a base station 104. The base station 104 is in communication with a high speed network 106 and PTT communications received from the communication device 102 is sent through the base station 104 and the network 106 to a packet data service node (PDSN). The PDSN communicates with the high speed network 106 and an application server's network 108, which is connected to a PTT network 110. The PDSN forwards the PTT communications to an application server 112 in the PTT network 110.
The application server 112 receives a PTT communication from one member and forwards it to all members of the PTT group. The PTT communication is usually received as data packets from the network 110, and the PTT communication sent out by the application server 112 are also in data packet format. A receiving mobile switching center (MSC) and a connected base station (BS) then established a dedicated channel to transmit the PTT communication to a receiving mobile client (a PTT member).
FIG. 2 illustrates a prior art message flow 200 for a PTT call set up. When a PTT user (originator) is ready to make a PTT communication, he presses a PTT activation button on his mobile device 102 and a PTT request is thus made. In response to the PTT request received by the mobile device 102, and the mobile device sends a call request message to the application server 112, which is also known as the PTT dispatcher. The application server 112 receives and processes the call request message. The call request processing includes identifying the PTT user, identifying a PTT group to which the PTT user belongs, identifying member of this PTT group, and preparing announce call messages to be sent to each member of the PTT group.
After the application server 112 sends the announce call messages, each announce call message is received by a MSC and forwarded by the MSC to a BS. The BS broadcasts the announce call message. If a mobile client who is a targeted receiver is available, the mobile client sends an accept call message back to the application server 112. After receiving the accept call message from at least one mobile client, the application server 112 sends a floor grant message back to the originating mobile client. There may be more than one targeted user in the originator's PTT communication group, and the application server 112 will grant the floor to the originator if there is at least one targeted mobile client available. After receiving the floor grant message, the PTT requesting mobile client (originator) can then make a PTT communication. The PTT related messages described above are transmitted as data packets, preferably as Internet Protocol (IP) data packets. Other data formats can also be used to transfer these PTT related messages.
The PTT communication set up process described above is time sensitive and the initial PTT latency shown in FIG. 2 is affected by network traffic. The long latency directly affects users of the PTT communication. Therefore, it is desirous to have a system and method for reducing the PTT latency and it is to such system and method this invention is primarily directed.